The present invention relates to a composition for use in a transparent and electrically conductive film and a method for making the film and more particularly to a composition for a transparent and electrically conductive film formed on a glass substrate or a ceramic substrate and a method for making the film.
Hitherto, an electrode material having a high transmittance for a visible light has been used in a display element such as a liquid crystal display and an electroluminesence display and in a heating resistor for preventing the window glass of a car, an air plane and building from collecting moisture or from freezing.
There has been known a transparent and electrically conductive material which usually consisted of antimony tin oxide(ATO) or indium tin oxide(ITO). These metal oxides can be applied to the glass substrate or a ceramic substrate for formation of a transparent and electrically conductive film.
The transparent and electrically conductive film can be formed by the following methods: (1) vacuum deposition method; (2) sputtering method; (3) CVD method; (4) screen printing method and (5) dipping method.
However, the above methods (1), (2) and (3) require a complicated equipment in a high cost and have a problem in the cost and the mass production. The methods (4) and (5) have a possibility to solve the problem due to the methods (1), (2) and (3), but have difficulty to form a film superior in the practical use.
For example, a use of organic solution of an inorganic compound such as indium nitrate, indium chloride or stannic chloride causes the formed film to generate a white spot or to have a weak mechanical strength which results in an easy scratching. There is a method to use an indium organic acid compound having a strong ion bonding such as indium octylate. Since the organic indium compound tends to be hydrolized and is relatively easy to be chemically changed, it is disadvantageous that the application method of liquid generates a gel state. Further, there is proposed another method to use an organic complex of indium or tin. In this method, an evaporation of tin compound during the heat treatment accompanied with thermal decomposition of the film applied to the glass substrate prevents the resultant film from forming a uniform structure. It is difficult for this method to obtain a uniform film having a low electric resistance.